Observation and modelling of stimulated Raman
scattering driven by an optically smoothed laser beam in
experimental conditions relevant for shock ignition

Year: 2021

Authors: Cristoforetti G., Hüller S., Koester P., Antonelli L., Atzeni S., Baffigi F., Batani D., Baird C.,
Booth N., Galimberti M., Glize K., Héron A., Khan M., Loiseau P., Mancelli D., Notley M., Oliveira P., Renner O., Smid M., Schiavi A., Tran G., Woolsey N.C., Gizzi LA.

Autors Affiliation: CNR, INO, Intense Laser Irradiat Lab, I-56124 Pisa, Italy; Ecole Polytech, CNRS, IP Paris, Ctr Phys Theor CPHT, F-91128 Palaiseau, France; Univ York, York Plasma Inst, Dept Phys, York YO10 5DD, N Yorkshire, England; Univ Roma La Sapienza, Dipartimento SBAI, I-00161 Rome, Italy; Univ Bordeaux, CNRS, CEA, CELIA, F-33405 Talence, France; Cent Laser Facil, STFC Rutherford Appleton Lab, Didcot SN2 1SZ, Oxon, England; Shanghai Jiao Tong Univ, Key Lab Laser Plasmas MOE, Shanghai 200240, Peoples R China; CEA, DAM, DIF, F-91297 Arpajon, France; Univ Paris Saclay, CEA, LMCE, F-91680 Bruyeres Le Chatel, France; Czech Acad Sci, Inst Plasma Phys, ELI Beamlines, Inst Phys, Prague 18221, Czech Republic; Helmholtz Zentrum Dresden Rossendorf, D-01328 Dresden, Germany.

Abstract: We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility, aimed
at investigating laser–plasma interaction in conditions that are of interest for the shock ignition scheme in inertial
confinement fusion (ICF), that is, laser intensity higher than 1016 W/cm2 impinging on a hot (T > 1 keV),
inhomogeneous and long scalelength pre-formed plasma. Measurements show a significant stimulated Raman scattering
(SRS) backscattering (∼ 4%−20% of laser energy) driven at low plasma densities and no signatures of two-plasmon
decay (TPD)/SRS driven at the quarter critical density region. Results are satisfactorily reproduced by an analytical
model accounting for the convective SRS growth in independent laser speckles, in conditions where the reflectivity is
dominated by the contribution from the most intense speckles, where SRS becomes saturated. Analytical and kinetic
simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau
damping and by filamentation of the most intense laser speckles. The absence of TPD/SRS at higher densities is
explained by pump depletion and plasma smoothing driven by filamentation. The prevalence of laser coupling in the
low-density profile justifies the low temperature measured for hot electrons (7−12 keV), which is well reproduced by
numerical simulations.

Journal/Review: HIGH POWER LASER SCIENCE AND ENGINEERING

Volume: 9      Pages from: e60  to: e60

More Information: The authors acknowledge financial support from the LASERLAB-EUROPE Access to Research Infrastructure activity within the EC´s seventh Framework Program (Application No. 18110033). This work has also been carried out within the framework of the EUROfusion Enabling research projects AWP19-20-ENR-IFE19.CEA01 and AWP21-ENR-01-CEA-02, and has received funding from the Euratom research and training programme 20192020 and 2021-2025 under grant No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. The authors also acknowledge financial support from the CNR-funded Italian research Network ELI-Italy (D.M. No. 631 08.08.2016) and the Czech Ministry of Education, Youth and Sports, project LTT17015.
KeyWords: Laser-Plasma Interaction, Kinetic simulations, Inertial Confinement Fusion
DOI: 10.1017/hpl.2021.48

Citations: 16
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